A number of different printing methods are used in printing presses. Non-impact printing (NIP) methods are understood as printing methods that do not require a fixed, that is to say, a physically unalterable printing forme. Printing methods of this type are able to produce different printed images in each printing operation. Examples of non-impact printing methods include ionographic methods, magnetographic methods, thermographic methods, electrophotography, laser printing, and in particular inkjet printing methods. Such printing methods typically involve at least one image producing device, for example at least one print head. In the inkjet printing method, such a print head is configured, for example, as an inkjet print head and has at least one and preferably a plurality of nozzles, by means of which at least one printing fluid, for example in the form of ink droplets, can be transferred selectively onto a printing substrate. Alternative printing methods, such as intaglio printing, planographic printing, offset printing and letterpress printing methods, in particular flexographic printing, use fixed printing formes. Depending upon the size of the print run and/or other requirements such as print quality, a non-impact printing method or a printing method that uses a fixed printing forme may be preferable.
The precise matching of a printed image on the front and back sides of a printing substrate that is printed on both sides is referred to as register (DIN 16500-2). In multicolor printing, the merging of individual printed images of different colors in precise alignment to form a single image is referred to as color registration (DIN 16500-2). In inkjet printing, as with other processes, appropriate measures must be implemented to maintain color registration and/or register. In particular, it is important for the relative position between print head and printing substrate to be known and/or kept constant. Registration is also referred to as color register. In the following, the term register mark will therefore also be understood as referring to a registration mark, i.e. a mark for checking color registration or color register.
Sheet-fed printing presses are known. However, conventional transport systems cannot always be used with particularly thick sheets.
From DE 10 2015 111525 A1, a sheet-fed printing press is known, which operates according to the principle of offset printing and which is equipped with additional inkjet printing elements that have print heads and dryers, which are optionally arranged so as to be movable. Drives for transporting sheets are not described.
From DE 102 27241 A1, a drive system of a sheet-fed printing press is known, in which drive control units act as module control units.
From DE 10 2011 088776 B3, a printing press that has inkjet print heads and dryers is known. The transport of printing substrate and drives provided for said transport are described only in connection with a web-fed printing press.
EP 0669208 A1 discloses a sheet-fed printing press having drive motors for cylinders and the capability of positioning said drives axially.
EP 0615941 A1 discloses a sheet-fed printing press having individually driven acceleration means.
From DE 697 21715 T2, a method and a device are known, in which mailpieces, in particular postcards, are singulated and fed to an inkjet print head. The mailpieces are accelerated to a first speed by a primary acceleration means and are accelerated to a second speed by a secondary acceleration means. The two acceleration means are driven by a common drive. A motor controller controls this drive as well as a drive that transports the mailpieces past the print head module. The mailpieces are decelerated by the secondary accelerator as needed in order to increase the gap between a mailpiece and the mailpiece that precedes it. Because of the common drive, decelerating this secondary acceleration means also necessarily decelerates the first acceleration means.
US 2001/0022422 A1 and US 2013/0216291 A1 each disclose a method and a copying machine by which paper sheets are removed from a pile from above, singulated, and fed to a printing couple.
US 2002/0180138 A1 discloses a method and a device in which checks are singulated and marked. A primary acceleration means is operated more slowly than a secondary acceleration means. The checks are decelerated or accelerated by the secondary acceleration means as needed in order to adjust the gap between a check and the check that precedes it. At the same time, the primary acceleration means is decelerated or accelerated in the same ratio.
U.S. Pat. No. 5,074,539 A discloses a substrate supply system having an acceleration means for singulating sheets from the bottom side of a sheet pile.
From DE 10152464 A1, a printing press is known, which operates based upon an inkjet printing method and in which each ink is assigned a separate module, wherein either each of the modules has its own drive or every two modules are assigned a common drive. Each module has its own drying device.
From EP 2946937 A1 a printing press is known, in which an inkjet printing module comprises in succession at least one application point for coating medium, at least one dryer, at least one additional application point for coating medium, and at least one additional dryer. Print heads can be retracted in a vertical direction.